CN104411800B - The method preparing birefringent polymer film - Google Patents

Abstract

The present invention relates to prepare the method for polymeric film, and such polymeric film is used for decoration or safety applications as both alignment layers or the purposes of retardation film in liquid crystal display (LCD) or other optics or electro-optical device.

Description

Method for producing birefringent polymer films

Technical Field

The present invention relates to a process for the preparation of a polymer film, the film so prepared, and the use of such a polymer film in Liquid Crystal Displays (LCD) or other optical or electro-optical devices for decorative or security applications such as alignment layers or optical retardation films.

Background and Prior Art

Optical compensators are used to improve the optical properties of Liquid Crystal Displays (LCDs), such as contrast ratio and grey scale representation at large viewing angles. For example, in TN or STN type uncompensated displays, gray scale variations, even gray scale inversion, as well as loss of contrast and undesirable color gamut variations are typically observed at large viewing angles.

An overview of the principles and methods of LCD technology and LCD optical compensation is given in US5,619,352, the entire disclosure of which is incorporated by reference into the present application.

As described in US5,619,352, the contrast of the display at wide viewing angles can be improved by a negatively birefringent C-plate compensator. However, such compensators do not improve the gray scale representation of the display. On the other hand, US5,619,352 proposes the use of birefringent O-plate compensators to suppress or even eliminate gray level inversion and improve gray level stability.

The terms "O-plate" and "a-plate" as used in US5,619,352 and throughout the present invention have the following meanings. An "O-plate" is an optical retarder that utilizes a layer of positively birefringent (e.g., liquid crystal) material with its primary optical axis oriented at an oblique angle relative to the plane of the layer.

An "a-plate" is an optical retarder utilizing a layer of uniaxially birefringent material with its extraordinary axis oriented parallel to the plane of the layer and its ordinary axis (also called "a-axis") oriented perpendicular to the plane of the layer (i.e. parallel to the normal direction of the incident light).

As the O-plate retarder, for example, an optical retardation film including a liquid crystal or mesomorphic material layer having a tilt structure may be used. As an a-plate retarder, the optical retardation film may comprise a positively birefringent liquid crystal or mesogenic material with planar orientation.

Those retardation films are commonly used in liquid crystal displays to switch between linear and circularly polarized light. The skilled person knows that a layer of reactive mesogens can be created to provide such a retardation layer. For example, RMS03001 (from Merck KGaA, Darmstadt, Germany), which is a commercially available reactive mesogen solution, can be spin-coated and photopolymerized to provide a planar aligned nematic film. By varying the coating conditions, films of different thicknesses can be produced, thus producing half-wave and quarter-wave retardation films.

Typically, the layer of reactive mesogens requires an alignment layer or rubbed plastic substrate to align in a planar state. In this regard, two main approaches are currently used in the display industry to align liquid crystals for optical film applications:

a rubbing process in which the plastic substrate or alignment layer is rubbed in one direction to provide an alignment direction for the coated liquid crystal. The alignment quality varies depending on the rubbing process and the characteristics of the substrate or film. The rubbing process is difficult to optimize and may produce different results. Furthermore, the rubbing process is considered a disadvantageous process by LCD manufacturers because it can generate particles that are difficult to control in advanced cleanrooms.

(ii) a photoalignment process, as described in US 7,364,671B2, wherein the dichroic photoinitiator is photoaligned while maintaining conditions that substantially inhibit polymerization or crosslinking of the polymerizable liquid crystal material. The photoalignment and polymerization steps are performed in two different steps and under different conditions. Therefore, such a photo-alignment layer may be difficult to prepare because the requirements of the preparation conditions must be adjusted in consideration of the respective compositions of the respective liquid crystal materials. Furthermore, an annealing step is usually required to allow the liquid crystals to fully align. Therefore, the photoalignment layer according to this process is expensive.

Thus, there remains a need for alternative manufacturing methods that do not have, or to a lesser extent do, the disadvantages of the prior art methods.

It is an object of the present invention to provide a one-step method of manufacturing an optical compensator which

a) Is particularly suitable for mass production,

b) suitable for use with a wide range of polymerisable liquid crystal materials,

c) no alignment layer such as a rubbed polyimide layer is required,

d) allowing the patterning of the polymer film to be carried out,

e) allowing the selected layer to be applied without the need for an additional alignment layer, and

f) allowing the production of thick films with uniform alignment.

Other objects of the present invention will be immediately apparent to those skilled in the art from the following detailed description.

Surprisingly, the inventors have found that the above problems can be solved by the present invention, which no longer requires an alignment layer or rubbing process to provide liquid crystal alignment for a planar aligned optical film, and which provides a method of producing a planar or obliquely aligned film without the need for an alignment layer and/or rubbing.

Polymer films can be created from reactive mesogens coated in an isotropic phase. A polarization state sensitive photoinitiator is required to be combined with UV polarized light and heat to induce planar or tilted alignment in the resulting optical film. The method of making such films can be done in one step using heat and polarized UV light. Thus, they can be coated on many different substrates (e.g., flat glass, color filters, plastic substrates) without further processing, resulting in, for example, a flat a-type retarder film or an inclined O-type retarder film.

Summary of The Invention

The present invention relates to a process for preparing a polymer film comprising, preferably consisting of:

a) providing a layer of polymerizable liquid crystal material comprising at least one dichroic photoinitiator on a substrate,

b) liquid crystal material in its isotropic phase upon irradiation with linearly polarized light, and

c) optionally removing the polymerized film from the substrate.

The invention also relates to a polymer film obtainable from the process as described above and below.

The invention further relates to the use of a polymer film as described above and below in Liquid Crystal Displays (LCDs) or other optical or electro-optical devices for decorative or security applications such as alignment layers or optical retardation films.

Such optical and electro-optical devices include, but are not limited to, electro-optical displays, Liquid Crystal Displays (LCDs), polarizers, compensators, beam splitters, reflective films, alignment films, color filters, holographic elements, hot stamped foils, color images, decorative or security markings, liquid crystal pigments, adhesive layers, non-linear optical (NLO) devices, and optical information storage devices.

The invention also relates to a compensator comprising at least one polymer film as described above and below.

The invention also relates to an LCD comprising at least one polymer film as described above and below.

Terms and definitions

As used herein, the term "polymer" will be understood to mean a molecule comprising a backbone of one or more different types of repeating units (the smallest constitutional unit of the molecule) and includes the commonly known terms "oligomer", "copolymer", "homopolymer", and the like. Furthermore, it is also understood that the term polymer includes, in addition to the polymer itself, initiator residues, catalysts and other elements that accompany the synthesis of the polymer, wherein these residues are understood not to be covalently bound thereto. In addition, these residues and other elements, which are usually removed in purification treatments after polymerization, are usually mixed or blended with the polymer so that they generally remain with the polymer when it is transferred between vessels or between solvents or dispersion media.

The term "polymerization" means a chemical process by which a plurality of polymerizable groups or polymer precursors (polymerizable compounds) containing such polymerizable groups are bonded together to form a polymer.

The terms "film" and "layer" include rigid or flexible, self-supporting or mechanically stable free-standing films, as well as coatings or layers on a supporting substrate or between two substrates.

The term "Liquid Crystal (LC)" relates to materials having a liquid crystalline mesophase in certain temperature ranges (thermotropic LC) or in certain concentration ranges in solution (lyotropic LC). They necessarily contain mesogenic compounds.

The terms "mesogenic compound" and "liquid crystalline compound" refer to compounds comprising one or more rod-shaped (rod-shaped or plate/lath-shaped) or disc-shaped (discotic) mesogenic groups. The term "mesogenic group" refers to a group that has the ability to induce liquid crystal phase (or mesogenic phase) behavior.

The compounds comprising mesogenic groups do not necessarily have to exhibit a liquid crystalline mesophase per se. It is also possible that they exhibit a liquid crystalline mesophase only in mixtures with other compounds, or when mesogenic compounds or materials or mixtures thereof are polymerized. This includes low molecular weight non-reactive liquid crystalline compounds, reactive or polymerizable liquid crystalline compounds, and liquid crystalline polymers.

The rod-like mesogenic groups typically comprise a mesogenic core consisting of one or more aromatic or non-aromatic cyclic groups directly connected to each other or via a linking group, optionally comprising end groups attached to the ends of the mesogenic core, and optionally comprising one or more side groups attached to the long side of the mesogenic core, wherein the end groups and side groups are typically selected from e.g. carbon-or hydrocarbon-based, polar groups (like halogen, nitro, hydroxyl etc.) or polymerizable groups.

The term "reactive mesogen" refers to a polymerizable mesogen or liquid crystal compound, preferably a monomeric compound. These compounds can be used as pure compounds or as mixtures of reactive mesogens with other compounds acting as photoinitiators, inhibitors, surfactants, stabilizers, chain transfer agents, non-polymerizable compounds, etc.

Polymerizable compounds having one polymerizable group are also referred to as "mono-reactive" compounds, compounds having two polymerizable groups are "di-reactive" compounds, and compounds having more than two polymerizable groups are "multi-reactive" compounds. Compounds without polymerizable groups are also referred to as "non-reactive or non-polymerizable" compounds.

The term "chiral" is generally used to describe an object that is not superimposable with its mirror image. An "achiral" (achiral) object is the same object as its mirror image.

Helical pitch (P) induced by chiral substances₀) In a first approximation inversely proportional to the concentration (c) of the chiral material used.

Helical pitch (P) induced by chiral substances₀) In a first approximation inversely proportional to the concentration (c) of the chiral material used. The proportionality constant of this relationship is called the Helical Twisting Power (HTP) of the chiral species and is defined by equation (1).

HTP＝1/(c·P₀) (1)

As with conventional photoinitiators, "dichroic photoinitiators" dissociate when exposed to an appropriate wavelength and the free radicals formed initiate polymerization of the monomer. Dichroic photoinitiators have the property that light absorption depends on the molecular orientation of the molecules. Dichroic photoinitiators selectively dissociate when aligned with the electric field vector of the incident light.

Light in the form of a plane wave in space is considered to be linearly polarized.

Visible light is electromagnetic radiation having a wavelength ranging from about 400nm to about 740 nm. Ultraviolet (UV) light is electromagnetic radiation having a wavelength range of about 200nm to 450 nm.

Emittance (E)_e) Or radiant power is defined as the power of electromagnetic radiation (do θ) incident on the surface per unit area (dA):

E_e＝dθ/dA (2)

radiation exposure or radiation dose (H)_e) StatorMeaning degree of radiation or radiation power (E)_e) Multiplication by time (t):

H_e＝E_e·t (3)

all temperatures, such as the melting point T (C, N) or T (C, S), the transition T (S, N) from smectic (S) to nematic (N) phase and the clearing point T (N, I) of the liquid crystal are indicated in degrees celsius. All temperature differences are expressed in degrees of difference. The term "clearing point" refers to the temperature at which the transition occurs between the mesophase having the highest temperature range and the isotropic phase.

The term "director" is known in the art and means the preferred direction of orientation of the long molecular axis (in the case of rod-like compounds) or the short molecular axis (in the case of discotic compounds) of the liquid crystal or RM molecules. In the case of this uniaxial ordering of the anisotropic molecules, the director is the axis of anisotropy.

The term "alignment" or "orientation" relates to the alignment (alignment) of anisotropic units of a material, such as small molecules or macromolecular fragments, in a general direction called the "alignment direction". In an alignment layer of a liquid crystal or RM material, the liquid crystal director coincides with the alignment direction such that the alignment direction corresponds to the direction of the anisotropy axis of the material.

The term "homogeneous orientation" or "homogeneous alignment" of the liquid crystal or RM material, e.g. in a layer of the material, means that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of the liquid crystal or RM molecules are oriented substantially in the same direction. In other words, the lines of the liquid crystal directors are parallel.

Throughout this application, the alignment of the liquid crystal or RM layer is a uniform alignment unless otherwise specified.

The term "planar alignment" for example in a layer of liquid crystal or RM material means that the long molecular axes (in the case of calamitic compounds) or the short molecular axes (in the case of discotic compounds) of the liquid crystal or RM molecules are aligned substantially parallel to the plane of the layer.

The term "tilt alignment" e.g. in a layer of liquid crystal or RM material means that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of the liquid crystal or RM molecules are oriented at an angle θ ("tilt angle") between 0 and 90 ° with respect to the plane of the layer.

The term "a-plate/film" refers to an optical retarder utilizing a layer of uniaxially birefringent material with its extraordinary axis oriented parallel to the plane of the layer.

The term "O-plate/film" refers to an optical retarder utilizing a layer of uniaxially birefringent material with its extraordinary axis tilted at an angle relative to the plane of the layer.

The birefringence Δ n is defined as follows:

Δn＝n_e-n_o(4)

wherein n is_eRepresents an extraordinary refractive index and n_oIs the ordinary refractive index, and the average refractive index n_av.Given by:

n_av.＝((2n_o ²+n_e ²)/3)^1/2(5)

the average refractive index n can be measured using an Abbe refractometer_av.With the ordinary refractive index n_o. Δ n can then be calculated from the above equation.

If so, the definitions given in Angew. chem.2004,116,6340-6368 of C.Tschierske, G.Pelzl and S.Diele may be applied.

Brief description of the drawings

Fig. 1 schematically shows a method according to the invention, wherein 1 denotes a radiation source, 2 denotes unpolarized light, 3 denotes a wire grid polarizer, 4 denotes linearly polarized light, 5 denotes a polymerizable liquid crystal material, 6 denotes a substrate, 7 denotes a heating source, 8 denotes a heated nitrogen purge and α denotes a variable radiation angle.

FIG. 2 depicts the retardation curve of the polymer film of example 1

FIG. 3 depicts the retardation curve of the polymer film of example 2

FIG. 4 depicts the retardation curve of the polymer film of example 3

Fig. 5 depicts the retardation curve (angle dependence of the radiation source) of the polymer film of example 4.

Detailed description of the invention

Suitable polymerizable liquid crystal materials for use in the method according to the invention comprise at least one mono-, di-or multireactive polymerizable mesogenic compound and at least one dichroic photoinitiator.

All known dichroic photoinitiators are suitable for the method according to the present invention. Dichroic photoinitiators comprising alphｃA-amine groups as disclosed in EP- ｃA-1388538 are preferably used. Especially preferred are dichroic photoinitiators of formula I,

wherein,

p is a polymerizable group, and P is a polymerizable group,

sp is a spacer group or a single bond,

A¹¹independently of one another in each case independently of one another, are an aryl, heteroaryl, aliphatic or heterocyclic radical which is optionally substituted by one or more identical or different radicals L, preferably 1, 4-cyclohexylene or 1, 4-phenylene which is optionally substituted by one or more identical or different radicals L,

Z¹¹in each occurrence independently of each other, -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR⁰¹-、-NR⁰¹-CO-、-NR⁰¹-CO-NR⁰²、-NR⁰¹-CO-O-、-O-CO-NR⁰¹-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CR⁰¹-、-CY⁰¹＝CY⁰²-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond, preferably-COO-, -OCO-or a single bond,

Y⁰¹and Y⁰²Each representing H, F, Cl or CN independently of the other.

m is 0,1, 2 or 3, preferably 2 or 3,

r is 0,1, 2,3 or 4, preferably 0,1 or 2,

l is, independently of one another in each case in a plurality of occurrences, H, halogen, CN or optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 5C atoms, preferably H, halogen or CN, alkyl or alkoxy having 1 to 5C atoms,

R^11-13independently of one another, H, halogen, CN, NO₂，NCS，SF₅P-Sp-or a linear or branched alkyl group having 1 to 20C atoms, optionally mono-or polysubstituted with F, Cl, Br, I or CN, and wherein one or more non-adjacent CH groups₂The radicals being in each case independently of one another optionally substituted by-O-, -S-, -NR-⁰¹-、-SiR⁰¹R⁰²-、-CO-、-COO-、-OCO-、-OCO-O-、-NR⁰¹-CO-、-CO-NR⁰¹-、-NR⁰¹-CO-NR⁰²-、-S-CO-、-CO-S-、-CY⁰¹＝CY⁰²-or-C.ident.C-is replaced in such a way that O and/or S atoms are not directly bound to one another, preferably alkyl or alkoxy having 1 to 12C atoms, and

R⁰¹and R⁰²Independently of one another, H, or a linear or branched chain having 1 to 20C atoms, preferably 1 to 6C atomsAn alkyl group.

In this context, the term "carbyl" denotes a monovalent or polyvalent organic group comprising at least one carbon atom, either free from other atoms (such As-C.ident.C-) or optionally containing one or more other atoms such As N, O, S, P, Si, Se, As, Te or Ge (e.g. carbonyl and the like). "hydrocarbyl" means a carbyl group additionally containing one or more H atoms and optionally containing one or more heteroatoms such As N, O, S, P, Si, Se, As, Te or Ge. "halogen" means F, Cl, Br or I.

The carbyl or hydrocarbyl group may be a saturated or unsaturated group. Unsaturated groups are for example aryl, alkenyl or alkynyl groups. Carbyl or hydrocarbyl groups having more than 3C atoms can be linear, branched, and/or cyclic, and can also contain spiro and/or fused rings.

In this context, the terms "alkyl", "aryl", "heteroaryl" and the like also include multivalent groups such as alkylene, arylene, heteroarylene and the like. The term "aryl" denotes an aromatic carbon radical or a radical derived therefrom. The term "heteroaryl" denotes an "aryl" group containing one or more heteroatoms according to the above definition.

Preferred carbyl and hydrocarbyl radicals are optionally substituted alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 25, very preferably 1 to 18C atoms, optionally substituted aryl or aryloxy having 6 to 40, preferably 6 to 25C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkoxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 6 to 40, preferably 6 to 25C atoms. Further preferred carbyl and hydrocarbyl radicals are C₁-C₄₀Alkyl radical, C₂-C₄₀Alkenyl radical, C₂-C₄₀Alkynyl, C₃-C₄₀Allyl radical, C₄-C₄₀Alkyldienyl radical, C₄-C₄₀Polyalkenyl radical, C₆-C₄₀Aryl radical, C₆-C₄₀An alkylaryl group,C₆-C₄₀Arylalkyl radical, C₆-C₄₀Alkylaryloxy radical, C₆-C₄₀Arylalkoxy group, C₂-C₄₀Heteroaryl group, C₄-C₄₀Cycloalkyl radical, C₄-C₄₀Cycloalkenyl groups, and the like. Particularly preferred is C₁-C₂₂Alkyl radical, C₂-C₂₂Alkenyl radical, C₂-C₂₂Alkynyl, C₃-C₂₂Allyl radical, C₄-C₂₂Alkyldienyl radical, C₆-C₁₂Aryl radical, C₆-C₂₀Arylalkyl and C₂-C₂₀A heteroaryl group.

Further preferred carbyl or hydrocarbyl radicals are straight-chain, branched or cyclic alkyl radicals having 1 to 40, preferably 1 to 25, C atoms, which are unsubstituted or mono-or polysubstituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH groups₂The radicals may each independently be-C (R)^x)＝C(R^x)-、-C≡C-、-N(R^x) -, -O-, -S-, -CO-O-, -O-CO-O-are replaced in such a way that O and/or S are not directly linked to one another.

R^xPreferably represents H, halogen, a linear, branched or cyclic alkyl chain having 1 to 25C atoms, wherein, in addition, one or more nonadjacent C atoms may be replaced by-O-, -S-, -CO-O-, -O-CO-O-, and wherein one or more H atoms may be replaced by fluorine, an optionally substituted aryl or aryloxy group having 6 to 40C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40C atoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, tert-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2, 2-trifluoroethyl, perfluorooctyl, perfluorohexyl and the like.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl and the like.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl and the like.

Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy and the like.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, and the like.

Aryl and heteroaryl groups may be monocyclic or polycyclic, i.e. they may have one ring (e.g. phenyl) or two or more rings, which may also be fused (e.g. naphthyl) or covalently linked (e.g. biphenyl), or contain a combination of fused and linked rings. Heteroaryl contains one or more heteroatoms, preferably selected from O, N, S and Se.

Particularly preferred are mono-, bi-or tricyclic aryl groups having 2 to 25C atoms, and mono-, bi-or tricyclic heteroaryl groups having 6 to 25C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-or 7-membered aryl and heteroaryl, where, in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and/or S atoms are not directly connected to one another.

Preferred aryl radicals are, for example, phenyl, biphenyl, terphenyl, [1,1':3',1 ″)]Terphenyl-2' -yl, naphthyl, anthracenyl, binaphthyl, phenanthrene, pyrene, dihydropyrene,Perylene, tetraphenyl, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene and the like。

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2, 3-triazole, 1,2, 4-triazole, tetrazole, furan, thiophene, selenophene, thiophene, and,Oxazole, isoOxazole, 1, 2-thiazole, 1, 3-thiazole, 1,2,3-Oxadiazole, 1,2,4-Oxadiazole, 1,2,5-Oxadiazole, 1,3,4-Oxadiazole, 1,2, 3-thiadiazole, 1,2, 4-thiadiazole, 1,2, 5-thiadiazole, 1,3, 4-thiadiazole; 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3, 5-triazine, 1,2, 4-triazine, 1,2, 3-triazine, 1,2,4, 5-tetrazine, 1,2,3, 4-tetrazine, 1,2,3, 5-tetrazine; or fused groups, e.g. indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthoimidazole, phenanthroimidazole, pyridoimidazole, pyrazinoimidazole, quinoxalimidazole, benzoAzoles, naphthoAzoles, anthracenesAzole, phenanthroAzole,Different from each otherOxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo 5, 6-quinoline, benzo-6, 7-quinoline, benzo-7, 8-quinoline, benzisoquinoline, acridine, phenothiazine, thiopheneOxazines, benzopyridazines, benzopyrimidines, quinoxalines, phenazines, naphthyridines, azacarbazoles, benzocarbazoles, phenanthridines, phenanthrolines, thieno [2,3b ]]Thiophene, thieno [3,2b]Thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazolethiophene, or combinations of these groups. Heteroaryl groups may also be substituted with alkyl, alkoxy, thioalkyl, fluoro, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups include both saturated rings, i.e. those containing only single bonds, and also partially unsaturated rings, i.e. those containing also multiple bonds. The heterocycle contains one or more heteroatoms, preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups may be monocyclic, i.e. contain only one ring (e.g. cyclohexane), or polycyclic, i.e. contain a plurality of rings (e.g. decahydronaphthalene or bicyclooctane). Particularly preferred are saturated groups. Further preferred are mono-, bi-or tricyclic groups having 3 to 25C atoms, which optionally contain fused rings and are optionally substituted. Further preferred are 5-, 6-, 7-or 8-membered carbocyclic radicals in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH groups₂The radicals may be replaced by-O-and/or-S-.

Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiophene, pyrrolidine, 6-membered groups, such as cyclohexane, silane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1, 3-dioxane, 1, 3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo [1.1.1] pentane-1, 3-diyl, bicyclo [2.2.2] octane-1, 4-diyl, spiro [3.3] heptane-2, 6-diyl, octahydro-4, 7-methano-diindane-2, 5-diyl.

The aryl, heteroaryl, carbyl and hydrocarbyl radicals optionally having one or more substituents are preferably selected from the group consisting of silyl, sulfo, sulfonyl, formyl, amine, imine, nitrile, mercapto, nitro, halogen, C_1-12Alkyl radical, C_6-12Aryl radical, C_1-12Alkoxy, hydroxy, or combinations of these groups.

Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy; electron withdrawing groups such as fluoro, nitro or nitrile groups; or substituents which raise the glass transition temperature (Tg) in the polymer, particularly bulky groups such as tertiary butyl or optionally substituted aryl groups.

Preferred substituents, hereinafter also referred to as "L", are for example F, Cl, Br, I, OH, -CN, -NO₂、-NCO、-NCS、-OCN、-SCN、-C(＝O)N(R^x)₂、-C(＝O)Y¹、-C(＝O)R^x、-C(＝O)OR^x、-N(R^x)₂Wherein R is^xHaving the above-mentioned meanings, and Y¹Represents halogen, optionally substituted silyl, optionally substituted aryl or heteroaryl having 4 to 40, preferably 4 to 20, ring atoms, and straight-chain or branched alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25C atoms, wherein one or more H atoms may optionally be replaced by F or Cl.

"substituted silyl or aryl" preferably means substituted by halogen, -CN, R⁰、-OR⁰、-CO-R⁰、-CO-O-R⁰、-O-CO-R⁰or-O-CO-O-R⁰Wherein R is⁰Have the above-mentioned meanings.

Particularly preferred substituents L are, for example, F, Cl, CN, NO₂、CH₃、C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅And also phenyl.

In the formulae shown above and below, a substituted phenylene ring

Preferably, it is

Wherein L, identically or differently on each occurrence, has one of the meanings given above and below, and preferably F, Cl, CN, NO₂、CH₃、C₂H₅、C(CH₃)₃、CH(CH₃)₂、CH₂CH(CH₃)C₂H₅、OCH₃、OC₂H₅、COCH₃、COC₂H₅、COOCH₃、COOC₂H₅、CF₃、OCF₃、OCHF₂、OC₂F₅Or P-Sp-, very preferably F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃、OCF₃Or P-Sp-, very preferably F, Cl, CN, CH₃、C₂H₅、OCH₃、COCH₃、OCF₃Or P-Sp-, most preferably F, Cl, CH₃、OCH₃、COCH₃Or OCF₃。

The polymerizable group P is preferably selected from groups containing a C ═ C double bond or a C ≡ C triple bond, and groups suitable for ring-opening polymerization, such as oxetane or epoxy groups.

Very preferably, the polymerizable group P is selected from: CH (CH)₂＝CW¹-COO-、CH₂＝CW¹-CO-、CH₂＝CW²-(O)_k3-、CW¹＝CH-CO-(O)_k3-、CW¹＝CH-CO-NH-、CH₂＝CW¹-CO-NH-、CH₃-CH＝CH-O-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH-CH₂)₂CH-OCO-、(CH₂＝CH)₂CH-O-、(CH₂＝CH-CH₂)₂N-、(CH₂＝CH-CH₂)₂N-CO-、CH₂＝CW¹-CO-NH-、CH₂＝CH-(COO)_k1-Phe-(O)_k2-、CH₂＝CH-(CO)_k1-Phe-(O)_k2-, Phe-CH ═ CH-, in which W¹Represents H, F, Cl, CN, CF₃Phenyl or alkyl having 1 to 5C atoms, especially H, F, Cl or CH₃，W²Represents H or an alkyl group having 1 to 5C atoms, in particular H, methyl, ethyl or n-propyl, W³And W⁴Each independently of the other H, Cl or an alkyl radical having 1 to 5C atoms, Phe denotes a1, 4-phenylene radical which is optionally substituted by one or more radicals L as defined above, but is different from P-Sp-, and k₁、k₂And k₃Each independently of the other represents 0 or 1, k₃Preferably represents 1, k₄Is an integer from 1 to 10.

Particularly preferred radicals P are CH₂＝CH-COO-、CH₂＝C(CH₃)-COO-、CH₂＝CF-COO-、CH₂＝CH-、CH₂＝CH-O-、(CH₂＝CH)₂CH-OCO-、(CH₂＝CH)₂CH-O-、Andin particular vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy groups, most preferably acrylate or methacrylate groups.

In a further preferred embodiment of the present invention, all polymerizable compounds and their corresponding subformulae comprise one or more branched groups (polyreactive polymerizable groups) comprising two or more polymerizable groups P instead of one or more groups P-Sp-. Suitable groups of this type, as well as polymerizable compounds containing them, are described, for example, in US 7,060,200B1 or US 2006/0172090 a 1. Particularly preferred are multireactive polymerizable groups selected from the following formulae:

-X-alkyl-CHP¹-CH₂-CH₂P²I*a

-X-alkyl-C(CH₂P¹)(CH₂P²)-CH₂P³I*b

-X-alkyl-CHP¹CHP²-CH₂P³I*c

-X-alkyl-C(CH₂P¹)(CH₂P²)-C_aaH_2aa+1I*d

-X-alkyl-CHP¹-CH₂P²I*e

-X-alkyl-CHP¹P²I*f

-X-alkyl-CP¹P²-C_aaH_2aa+1I*g

-X-alkyl-C(CH₂P¹)(CH₂P²)-CH₂OCH₂-C(CH₂P³)(CH₂P⁴)CH₂P⁵I*h

-X-alkyl-CH((CH₂)_aaP¹)((CH₂)_bbP²) I*i

-X-alkyl-CHP¹CHP²-C_aaH_2aa+1I*k

wherein

"alkyl" represents a single bond, or a straight or branched alkylene group having 1 to 12C atoms, wherein one or more non-adjacent CH groups₂Each radical, independently of the others, may be substituted by-C (R)^x)＝C(R^x)-、-C≡C-、-N(R^x) -, -O-, -S-, -CO-O-, -O-CO-O-in such a way that O and/or S atoms are not directly linked to one another, and wherein, in addition, one or more H atoms may be replaced by F, Cl or CN, wherein R is^xHas the above-mentioned meaning and preferably represents R as defined above⁰。

aa and bb each, independently of one another, denote 0,1, 2,3,4, 5 or 6,

x has one of the meanings indicated for X', and

P^1-5each independently of the others, has one of the meanings indicated above for P.

Preferred spacer groups Sp are selected from the formula Sp '-X', such that the group "P-Sp-" corresponds to the formula "P-Sp '-X' -", wherein

Sp' represents an alkylene group having 1 to 20, preferably 1 to 12C atoms, which is optionally mono-or polysubstituted with F, Cl, Br, I or CN, and wherein, in addition, one or more non-adjacent CH groups₂The radicals may each, independently of one another, be-O-, -S-, -NH-, -NR-⁰¹-、-SiR⁰¹R⁰²-、-CO-、-COO-、-OCO-、-OCO-O-、-S-CO-、-CO-S-、-NR⁰¹-CO-O-、-O-CO-NR⁰¹-、-NR⁰¹-CO-NR⁰¹-, -CH-or-C.ident.C-in such a way that O and/or S atoms are not bonded directly to one another,

x' represents-O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR⁰¹-、-NR⁰¹-CO-、-NR⁰¹-CO-NR⁰¹-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CR⁰¹-、-CY⁰¹＝CY⁰²-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond,

R⁰¹and R⁰²Each independently of the other represents H or an alkyl radical having 1 to 12C atoms, and

Y⁰¹and Y⁰²Each representing H, F, Cl or CN independently of the other.

X' is preferably-O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR-⁰-、-NR⁰¹-CO-、-NR⁰¹-CO-NR⁰¹-or a single bond.

A typical spacer Sp' is, for example, - (CH)₂)_p1-、-(CH₂CH₂O)_q1-CH₂CH₂-、-CH₂CH₂-S-CH₂CH₂-、-CH₂CH₂-NH-CH₂CH₂-or- (SiR)⁰¹R⁰²-O)_p1-, where p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R⁰¹And R⁰²Have the above-mentioned meanings.

A particularly preferred group-X '-Sp' -is- (CH)₂)_p1-、-O-(CH₂)_p1-、-OCO-(CH₂)_p1-、-OCOO-(CH₂)_p1-。

Particularly preferred radicals Sp' are in each case, for example, linear ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkenylene, vinylene, propenylene and butenylene.

The compounds of the formula I, which can preferably be used in the process according to the invention, are the following

Wherein L is H or F, R¹¹Is alkyl or alkoxy having 1 to 12C atoms, R¹²And R¹³Selected from alkyl or alkoxy groups having 1 to 6C atoms, very preferably methyl, ethyl or propyl.

The most preferred dichroic photoinitiators for use in the process according to the present invention are compounds of formula I-2, wherein L is F, R¹¹Is an alkyl radical of 1 to 12C atoms, R¹²And R¹³Selected from alkyl groups, very preferably methyl, ethyl or propyl.

In preferred liquid crystal materials for use in the method according to the invention, the proportion of dichroic photoinitiator is preferably in the range of 1-40 wt%, more preferably in the range of 1-30 wt%, even more preferably in the range of 1-20 wt%.

Preferably, the polymerizable liquid crystal material used in the method according to the invention is a mixture of two or more, e.g. 2 to 25, liquid crystal compounds.

The method according to the invention is not limited to a specific liquid crystal material but can in principle be used for the alignment of all RMs known from the prior art. The RM is preferably selected from rod-like or discotic compounds exhibiting thermotropic or lyotropic liquid crystallinity, very preferably rod-like compounds, or mixtures of one or more types of these compounds having a liquid crystalline mesophase in a certain temperature range. These materials generally have good optical properties, such as reduced chroma, and can be easily and quickly aligned to the desired orientation, which is particularly important for large-scale industrial production of polymer films. The liquid crystal may be a small molecule (i.e., a monomeric compound) or a liquid crystal oligomer.

Preferably, the polymerizable liquid crystalline material used in the method according to the invention preferably comprises at least one mono-reactive polymerizable mesogenic compound, at least one di-or multireactive polymerizable mesogenic compound, and at least one dichroic photoinitiator.

Suitable polymerizable liquid crystal materials according to the present invention comprise polymerizable mono-, di-or multireactive compounds selected from formula II

P-Sp-MG-R⁰II

Wherein

P is a polymerizable group, preferably an acryloyl group, methacryloyl group, vinyl group, vinyloxy group, propenyl ether group, epoxy group, oxetanyl group or styryl group,

sp is a spacer group or a single bond,

MG is a rod-like mesogenic group, preferably selected from the group consisting of formula M,

m is- (A)²¹-Z²¹)_k-A²²-(Z²²-A²³)_l-，

A²¹To A²³Independently of one another in each occurrence is an aryl, heteroaryl, heterocyclic or alicyclic group optionally substituted by one or more identical or different radicals L, preferably 1, 4-cyclohexylene or 1, 4-phenylene, 1, 4-pyridine, 1, 4-pyrimidine, 2, 5-thiophene, 2, 6-dithieno [3,2-b:2',3' -d ] optionally substituted by one or more identical or different radicals L]Thiophene, 2, 7-fluorine, 2, 6-naphthalene, 2, 7-phenanthrene,

Z²¹and Z²²Independently of one another at each occurrence, -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR⁰¹-、-NR⁰¹-CO-、-NR⁰¹-CO-NR⁰²、-NR⁰¹-CO-O-、-O-CO-NR⁰¹-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-、-N＝CH-、-N＝N-、-CH＝CR⁰¹-,-CY⁰¹＝CY⁰²-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond, preferably-COO-, -OCO-, -CO-O-, -O-CO-, -OCH₂-、-CH₂O-、-_,-CH₂CH₂-、-(CH₂)₄-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond,

l has the meaning as defined above in formula I,

R⁰is H, an optionally fluorinated alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy radical having 1 to 20C atoms, preferably 1 to 15C atoms, or is Y⁰Or P-Sp-,

Y⁰is F, Cl, CN, NO₂、OCH₃OCN, SCN, optionally fluorinated alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 4C atoms or mono-, oligo-or polyfluoroalkyl or alkoxy having 1 to 4C atoms, preferably F, Cl, CN, NO₂、OCH₃Or mono-, oligo-or polyfluoroalkyl or alkoxy having 1 to 4C atoms,

Y⁰¹and Y⁰²Each independently having the meaning as defined above in formula I,

R⁰¹and R⁰²Each independently has the meaning as defined above in formula I, and

k and l are each independently 0,1, 2,3 or 4, preferably 0,1 or 2, most preferably 1.

Suitable RMs are known to the person skilled in the art and are disclosed, for example, in WO 93/22397, EP 0261712, DE 19504224, WO 95/22586, WO 97/00600, US5,518,652, US5,750,051, US5,770,107 and US6,514,578. Suitable and preferred mono-, di-or multireactive RMs for use according to the invention are shown in the following table.

Wherein

P⁰Independently of one another in the case of a plurality of occurrences, is a polymerizable group, preferably an acryloyl group, a methacryloyl group, an oxetanyl group, an epoxy group, a vinyl group, a vinyloxy group, a propenyl ether group or a styryl group,

A⁰in each case independently of one another, are 1, 4-phenylene which is optionally substituted by 1,2,3 or 4 radicals L, or trans-1, 4-cyclohexylene,

Z⁰in the case of multiple occurrence are independently of one another-COO-, -OCO-, -CH₂CH₂-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond,

r is 0,1, 2,3 or 4, preferably 0,1 or 2,

t is, independently of one another, 0,1, 2 or 3 in the case of multiple occurrences,

u and v are independently of one another 0,1 or 2,

w is a number of 0 or 1,

x and y are each independently of the other 0, or identically or differently an integer from 1 to 12,

z is 0 or 1, wherein z is 0, if the adjacent x or y is 0,

and wherein the benzene and naphthalene rings may additionally be substituted by one or more identical or different groups L.

Parameter R⁰、Y⁰、R⁰¹、R⁰²And L has the same meaning as given in formula II above.

In another preferred embodiment, suitable polymerizable liquid crystal materials comprise at least one mono-reactive chiral polymerizable mesogenic compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound, and at least one dichroic photoinitiator.

In a particularly preferred embodiment, a suitable polymerizable liquid crystal material for use in the method of the present invention comprises at least one di-or multireactive chiral polymerizable mesogenic compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound, and at least one dichroic photoinitiator.

The mono-, di-or multireactive chiral polymerizable mesogenic compounds used according to the present invention preferably comprise one or more ring elements which are linked together by direct bonding or via a linking group and wherein two of these ring elements may optionally be linked to each other directly or via a linking group which may be the same or different from the linking group mentioned. The ring elements are preferably selected from four-, five-, six-or seven-membered rings, preferably five-or six-membered rings.

The helical twisting power (IHTP) of the polymerizable chiral compounds preferably used according to the invention, each used alone or in combination with one another_{General assembly}I) Is preferably 20 μm in absolute value^-1Or more, preferably 40 μm^-1Or more, more preferably at 60 μm^-1Or larger, most preferably 80 μm^-1Or more to 260 μm^-1Or smaller.

Suitable polymerizable chiral compounds and their synthesis are described, for example, in US 7,223,450, or are commercially available as Paliocolor(BASF AG)。

Preferred mono-, di-or multireactive chiral polymerisable mesogenic compounds for use according to the invention are selected from the following formulae

Wherein

P⁰Independently of one another in the case of a plurality of occurrences, is a polymerizable group, preferably an acryloyl group, a methacryloyl group, an oxetanyl group, an epoxy group, a vinyl group, a vinyloxy group, a propenyl ether group or a styryl group,

A⁰and B⁰In each case independently of one another, are 1, 4-phenylene which is optionally substituted by 1,2,3 or 4 radicals L, or trans-1, 4-cyclohexylene,

X⁰and Z⁰Independently of one another in the case of multiple occurrences of-COO-、-OCO-、-CH₂CH₂-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond,

r is a chiral alkyl or alkoxy group having 4 or more, preferably 4 to 12C atoms, such as 2-methylbutyl, 2-methyloctyl, 2-methylbutoxy or 2-methyloctyloxy,

ch is a chiral group selected from cholesterol, estradiol or terpenoid groups such as menthyl or citronellyl,

l has the meaning as defined above in formula I,

r is 0,1, 2,3 or 4, preferably 0,1 or 2,

t is, independently of one another, 0,1, 2 or 3,

u and v are independently of one another 0,1 or 2,

w is a number of 0 or 1,

x is independently of one another 0 or, identically or differently, an integer from 1 to 12,

z is 0 or 1, wherein z is 0, if the adjacent x or y is 0,

and wherein the benzene and naphthalene rings may additionally be substituted by one or more identical or different groups L.

In a preferred embodiment, the proportion of the mono-reactive polymerizable mesogenic compound (preferably selected from formulae II-1, II-13) in the total liquid crystalline material used in the process according to the invention is preferably in the range of from 20 to 90 wt.%, more preferably in the range of from 30 to 80 wt.% and even more preferably in the range of from 40 to 70 wt.%.

In another preferred embodiment, the proportion of the di-reactive polymerizable mesogenic compound (preferably selected from the formulae II-27) in the total liquid crystalline material used in the process according to the invention is preferably in the range of from 1 to 30 wt.%, more preferably in the range of from 1 to 20 wt.% and even more preferably in the range of from 1 to 10 wt.%.

In another preferred embodiment, the proportion of multireactive polymerizable mesogenic compound in the total liquid crystal material used in the process according to the invention is preferably in the range of 0 to 30 wt. -%, more preferably in the range of 0 to 20 wt. -% and even more preferably in the range of 0 to 10 wt. -%.

The proportion of chiral polymerisable mesogenic compound, preferably selected from the formula CR8, in the overall liquid crystal material used in the method according to the invention is preferably in the range of 0-30 wt.%, more preferably in the range of 0-20 wt.%, and even more preferably in the range of 0-10 wt.%.

In a particularly preferred embodiment, the polymerizable liquid crystalline material used according to the invention comprises at least one non-polymerizable chiral compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound and at least one dichroic photoinitiator.

Especially preferred are non-polymerizable chiral compounds having a high Helical Twisting Power (HTP), especially those disclosed in WO 98/00428. Further commonly used non-polymerizable chiral compounds are, for example, commercially available R/S-5011, R-811 or CB-15 (from Merck KGaA, Darmstadt, Germany).

In a preferred overall liquid crystal material for use in the method according to the invention, the proportion of the chiral non-polymerisable mesogenic compound is preferably in the range of 0-30 wt.%, more preferably in the range of 0-20 wt.%, and even more preferably in the range of 0-10 wt.%.

Suitable polymerisable liquid-crystalline materials for use in the method according to the invention may also comprise one or more dyes having an absorption maximum tuned to the wavelength of the radiation used for polymerisation, in particular UV dyes such as 4,4 "-azoxyanisole orDye (from Ciba AG).

The polymerizable liquid-crystalline materials used according to the invention may also comprise one or more stabilizers or inhibitors to prevent undesiredPreferably in an amount of 0-0.1%, very preferably 0-0.2%, for example selected from commercially availableSeries (Ciba AG), such as Irganox 1076.

In a preferred embodiment, suitable polymerisable liquid crystalline materials for use in the method according to the invention comprise one or more mono-reactive polymerisable non-mesogenic compounds, preferably in an amount of 0-50%, very preferably 0-20%. Typical examples are alkyl acrylates or methacrylates, preferably isobornyl methacrylate.

In another preferred embodiment, the polymerizable liquid crystalline material for use in the method according to the invention optionally comprises one or more di-or multireactive polymerizable non-mesogenic compounds, preferably in an amount of 0-50%, very preferably 0-20%, alternatively or in addition to said di-or multireactive polymerizable mesogenic compounds. Typical examples of di-reactive monomers are alkyl diacrylates or dimethacrylates or hexanediol diacrylates having alkyl groups of 1 to 20C atoms. Typical examples of multireactive monomers are trimethylpropane trimethacrylate or pentaerythritol tetraacrylate.

One or more chain transfer agents may also be added to the polymerizable liquid crystal material to alter the physical properties of the polymer film. Particularly preferred are thiol compounds, for example mono-reactive thiols such as dodecyl mercaptan, or poly-reactive thiols such as trimethylpropane tris (3-mercaptopropionate). Very preferred are mesogenic or liquid crystal thiols as disclosed, for example, in WO 96/12209, WO 96/25470 or US6,420,001. By using a chain transfer agent, the length of the free polymer chains and/or the length of the polymer chains between two crosslinks in the polymer film can be controlled. When the amount of the chain transfer agent is increased, the length of the polymer chain in the polymer film is decreased.

The polymerizable liquid crystalline material according to the present invention may also comprise a polymeric binder or one or more monomers capable of forming a polymeric binder, and/or one or more dispersing aids. Suitable binders and dispersing aids are disclosed, for example, in WO 96/02597. However, it is preferred that the polymerizable material be free of binders or dispersing aids.

The polymerizable liquid crystalline material may additionally comprise one or more additional components such as catalysts, sensitizers, stabilizers, inhibitors, chain transfer agents, co-reactive monomers, surface-active compounds, lubricants, wetting agents, dispersants, hydrophobing agents, binders, flow improvers, defoamers, deaerators, diluents, reactive diluents, auxiliaries, colorants, dyes or pigments.

The polymerizable liquid-crystalline materials used according to the invention are themselves prepared in a conventional manner, for example by mixing one or more of the above-described dichroic photoinitiators with one or more polymerizable compounds as defined above, and optionally with further liquid-crystalline compounds and/or additives. In general, the desired amount of the components used in lesser amounts is dissolved in the components making up the main constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent (for example in acetone, chloroform or methanol) and, after thorough mixing, to remove the solvent again, for example by distillation.

For the method of the present invention, particularly preferred polymerizable liquid crystalline materials comprise:

a) one or more achiral mono-, di-or multireactive polymerizable mesogenic compounds,

b) one or more dichroic photoinitiators in the form of one or more,

c) optionally one or more polymerizable chiral compounds,

d) optionally one or more stabilizers, and optionally one or more stabilizers,

e) optionally one or more mono-, di-or multireactive polymerizable non-mesogenic compounds,

f) optionally one or more non-polymerizable chiral compounds

g) Optionally one or more dyes that exhibit an absorption maximum at the wavelength used to initiate photopolymerization,

h) optionally one or more chain transfer agents,

i) optionally one or more stabilizers.

The polymerizable liquid crystalline material may be applied to the substrate by conventional coating techniques such as spin coating or doctor blading. It can also be applied by conventional printing techniques known to those skilled in the art, such as screen printing, offset printing, roll-to-roll printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, engraved gravure printing, transfer printing, heat seal printing, ink jet printing or printing with a stamp or plate.

The polymerizable liquid crystal material may also be dissolved in a suitable solvent. The solution is then coated or printed onto a substrate, for example by spin coating or printing or other known techniques, and the solvent is evaporated off prior to polymerization. In most cases, it is appropriate to heat the mixture to aid in solvent evaporation. As the solvent, for example, a standard organic solvent can be used. The solvent may for example be selected from ketones such as acetone, methyl ethyl ketone, methyl propyl ketone or cyclohexanone, acetates such as methyl, ethyl or butyl acetate or methyl acetoacetate, alcohols such as methanol, ethanol or isopropanol, aromatic solvents such as toluene or xylene, halogenated hydrocarbons such as di-or trichloromethane, glycols or their esters such as PGMEA (propylene glycol monomethyl ether acetate), gamma-butyrolactone and the like. Binary, ternary or higher mixtures of the above solvents may also be used.

As substrates for the process according to the invention, it is possible to use, for example, glass or quartz plates or plastic films or plates. Suitable and preferred plastic substrates are, for example, films of polyesters such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyvinyl alcohol (PVA), Polycarbonate (PC) or triacetyl cellulose (TAC), very preferably PET or TAC films. As the birefringent substrate, for example, a uniaxially stretched plastic film can be used. For example, a PET film isFrom DuPont Teijinfilms under the trade nameAnd (4) carrying out commercial purchase. Particularly preferred substrates are TAC, PET, PVA, PE films or glass plates.

Preferably, the coated substrate according to the invention is planar, but structured substrates such as fresnel lenses can also be used.

A second substrate may also be placed on top of the coated material before and/or during and/or after polymerization. The substrate may or may not be removed after polymerization. When two substrates are used, at least one of the substrates must be transparent to the actinic radiation used for polymerization. Isotropic or birefringent substrates may be used. After polymerization, it is preferred to use an isotropic substrate if the substrate is not removed from the polymer film.

The irradiation in step b) according to the invention is preferably carried out by exposing the polymerizable liquid crystalline material to linearly polarized actinic radiation. Actinic radiation means radiation with light, preferably UV light, IR light. In the method according to the invention, the radiation wavelength should be chosen such that it causes the dissociation of the dichroic photoinitiator and the polymerization of the polymerizable compound. In this respect, step b) is most preferably performed by exposing the polymerizable liquid crystalline material to linearly polarized UV radiation.

The radiation wavelength can be adjusted by a UV band-pass filter. The radiation wavelength is preferably in the range of 250nm to 450nm, more preferably in the range of 320nm to 390 nm. Particularly preferred is a radiation wavelength of about 365 nm.

As a source for UV radiation, for example a single UV lamp or a set of UV lamps may be used. When high power lamps are used, the curing time can be shortened. Another possible source for UV radiation is a laser.

The linear polarization of the actinic radiation can be achieved by methods known to the skilled worker. The preferred linear polarization is achieved by passing the radiation through a suitable linear polarizer (e.g., a commercially available dye-doped absorbing polarizer).

The irradiation in step b) according to the invention is carried out at a temperature wherein the polymerizable liquid crystalline material is in the isotropic phase. In a preferred embodiment, the irradiation is preferably carried out at a temperature of 1-10 ℃ above the clearing point, more preferably at a temperature of 1-5 ℃ above the clearing point, most preferably at a temperature of 1-3 ℃ above the clearing point.

The irradiation in step b) according to the invention is preferably carried out under an inert gas atmosphere, preferably under a heated nitrogen atmosphere, but irradiation in air is also possible.

As described above, the polymerizable liquid crystal material used in the present invention contains a dichroic photoinitiator. As with conventional photoinitiators, dichroic photoinitiators dissociate when exposed to a suitable wavelength, and the resulting group initiates polymerization of the monomer. The dichroic photoinitiator used in the polymerizable liquid crystal material of the present invention has a characteristic that its light absorption depends on the molecular orientation of molecules. Thus, when illuminated with said linearly polarized UV light, mainly polymerization initiating radicals are generated, wherein the local director is present parallel to the polarization direction. The local radical generation causes a difference in the local polymerization rate of the polymerizable liquid crystal material in the isotropic phase. The polymerization rate of the liquid crystal molecules aligned parallel to the electric field of the linearly polarized light is faster than that of the liquid crystal molecules aligned perpendicular to the electric field of the linearly polarized light. As a result, the difference in polymerization rate is prioritized over domain formation parallel to linearly polarized UV light, and birefringence is eventually induced into the polymer film due to complete polymerization and uniform orientation of the liquid crystal material in the polymer film.

The curing time depends, inter alia, on the reactivity of the polymerizable liquid-crystalline material, the thickness of the coating layer, the type of polymerization initiator and the power of the UV lamp. The curing time is preferably 5 minutes or less, very preferably 3 minutes or less, most preferably 1 minute or less. For mass production, short curing times of ≦ 30 seconds are preferred.

Suitable UV radiation powers are preferably in the range from 5 to 200mWcm^-2In the range of 50 to 175mWcm, more preferably 50 to 175mWcm^-2In the range of, and most preferably at 100-150mWcm^-2Within the range.

Suitable UV doses are preferably in the range 25-7200mJcm, with respect to the applied UV radiation and as a function of time^-2Within the range of more preferably 500-^-2In the range, and most preferably 3000-7200mJcm^-2Within the range.

In a preferred embodiment, the liquid crystal molecules in the polymer film are aligned in a planar orientation with respect to the main plane of the substrate. If the radiation source in step b) is positioned at an angle perpendicular to the main plane of the substrate, planar orientation of the liquid crystal molecules can be achieved in the resulting polymer film.

In another preferred embodiment, the liquid crystal material in the polymer film is oriented in a tilted alignment (>0 ° <90 °) with respect to the main plane of the substrate, which can be achieved if the radiation source is located at an oblique angle (>0 ° <90 °) with respect to the main plane of the substrate. Preferably, the radiation angle is >10 ° <80 °, more preferably >20 ° <70 °, or even more preferably >30 ° <60 °.

The invention also relates to a polymer film obtained by the process described above and below.

The oriented polymer film of the present invention can be used as a retardation or compensation film, for example in liquid crystal displays, to improve contrast and brightness at large viewing angles and to reduce chroma. They can be used outside the switchable liquid crystal cell in LCDs or between substrates (usually glass substrates), forming a switchable liquid crystal cell and containing a switchable liquid crystal medium (in-cell application).

Various types of optical retarders are known. For example, an "a-film" (or a-plate) is an optical retarder that utilizes a layer of uniaxially birefringent material with its extraordinary axis oriented parallel to the plane of the layer. In connection therewith, an "O-film" (or O-plate) is an optical retarder utilizing a layer of uniaxially birefringent material, the extraordinary axis of which is inclined at an angle with respect to the plane of the layer.

Depending on the irradiation angle as described above, the polymer film obtainable by the method according to the invention can be used as an a-plate (planar orientation of the liquid crystal molecules of the polymer film) if the radiation source in step b) is located at a perpendicular angle relative to the main plane of the substrate, or as an O-plate (oblique orientation of the liquid crystal molecules in the polymer film) if the radiation source is located at an oblique angle (>0 ° <90 °) relative to the main plane of the substrate.

The optical retardation of the polymer film ((λ)) as a function of the wavelength of the incident light beam (λ) is given by the following equation (6):

(λ)＝(2πn·d)/λ (6)

where (Δ n) is the birefringence of the film, (d) is the thickness of the film and λ is the wavelength of the incident beam.

According to Snellius' law, birefringence is defined as a function of the direction of an incident beam

Δn＝sinΘ/sinΨ (7)

Where sin Θ is the angle of incidence or the tilt of the optical axis in the membrane and sin Ψ is the corresponding angle of reflection.

Based on these laws, birefringence and, consequently, optical retardation, is substantially dependent on the thickness of the film and the tilt angle of the optical axis in the film (see Berek's compensator). Thus, the skilled artisan recognizes that different optical retardations or different birefringence may be produced by adjusting the orientation of the liquid crystal molecules in the polymer film.

The birefringence (Δ n) of the polymer film according to the present invention is preferably in the range of 0.01 to 0.30, more preferably in the range of 0.01 to 0.25, and even more preferably in the range of 0.01 to 0.16.

The thickness of the polymer film obtained by the method according to the present invention is preferably in the range of 3 to 30 μm, more preferably in the range of 3 to 20 μm, even more preferably in the range of 3 to 10 μm.

The optical retardation as a function of the tilt angle and the thickness of the polymer film obtained by the process according to the invention are less than 200nm, less than 180nm, and even more preferably less than 150 nm.

The present invention further relates to a method of making a polymer film comprising at least two regions having different birefringence, or a pattern comprising two or more regions having different birefringence. The change in birefringence results in a change in retardation in different regions of the film.

Such films may be prepared by a method as described above in which only selected portions of the polymerizable liquid crystal material are exposed to radiation, such as by using a photomask, or in which different portions of the polymerizable liquid crystal material are exposed to different intensities of radiation, such as by using a shadow mask having different regions that transmit radiation differently, or by using a radiation source having a variable intensity.

Especially preferred is a polymer film according to the invention comprising a pattern of one or more, preferably one, two or three, different areas with different retardation values, each of said values being adjusted such that its efficiency in converting linearly polarized light into circularly polarized light is optimized for light of one of the main colors red, green and blue (R, G, B). In particular, the retardation values correspond to a quarter of the wavelength of the respective color and are preferably as follows:

for red light at a wavelength of 600nm, the retardation is 140-190nm, preferably 145-180nm, very preferably 145-160nm, most preferably 150 nm.

For green light at a wavelength of 550nm, the retardation is 122-152nm, preferably 127-147nm, very preferably 132-142nm, most preferably 137 nm.

For blue light at a wavelength of 450nm, the retardation is 85-120nm, preferably 90-115nm, very preferably 100-115nm, most preferably 112 nm.

The retardation of the film can be varied, for example, by varying the intensity and/or duration of the radiation.

The polymer films of the present invention can also be used as alignment films for other liquid crystal or RM materials. For example, they may be used in LCDs to induce or improve alignment of switchable liquid crystalline media, or to align subsequent layers of polymerizable liquid crystalline material coated thereon. In this way, a laminate of polymerized liquid crystal films can be manufactured.

The polymer film of the present invention can be used in various types of liquid crystal displays, for example, displays having vertical alignment such as DAP (deformation of aligned phase), ECB (electrically controlled birefringence), CSH (color super homeotropic), VA (vertical alignment), VAN or VAC (vertically aligned nematic or cholesteric), MVA (multi-domain vertical alignment) or PVA (patterned vertical alignment) mode; displays with bend or hybrid alignment such as OCB (optically compensated bend box or optically compensated birefringence), R-OCB (reflective OCB), HAN (hybrid aligned nematic) or pi-cell (pi-cell) mode; displays with twisted orientation such as TN (twisted nematic), HTN (highly twisted nematic), STN (super twisted nematic), AMD-TN (active matrix driven TN) modes; displays of IPS (in-plane switching) mode or displays with switching in an optically isotropic phase.

The invention is described above and below with reference to preferred embodiments. It will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

Many of the compounds mentioned above and below and mixtures thereof are commercially available. All these compounds are known or can be prepared by processes known per se, as described in the literature (for example in standard works such as Houben-Weyl, Methoden der Organischen Chemistry [ Methods of Organic Chemistry ], Georg-Thieme-Verlag, Stuttgart), precisely under reaction conditions which are known and suitable for the reaction in question. These variants, known per se, can also be used, but are not described here in any further detail.

As used herein, plural forms of terms herein shall be construed to include the singular form and vice versa, unless the context clearly dictates otherwise.

Throughout this application, all concentrations are given in weight percent and refer to the respective mixtures as a whole, all temperatures being in degrees Celsius (C.) and differences in temperature being in degrees Celsius, unless explicitly stated otherwise. All Physical Properties have been determined according to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", StatusNov.1997, Merck KGaA, Germany and are given for 20 ℃ unless explicitly stated otherwise. Optical anisotropy (. DELTA.n) was measured at a wavelength of 589 nm.

Throughout the description and claims of this application, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other components. On the other hand, the term "comprising" also includes the term "consisting of … …" but is not limited thereto.

It will be appreciated that modifications may be made to the embodiments of the invention described above, while still falling within the scope of the invention. Each feature disclosed in this specification may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

All of the features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Likewise, features described in non-essential combinations may be used separately (not in combination).

The invention will now be described in more detail with reference to the following examples, which are merely illustrative and do not limit the scope of the invention.

Examples

Example 1

The following polymerizable liquid crystalline materials were prepared

Clearing the bright spots: 48.5 deg.C

The polymerizable liquid crystalline material was spin coated onto the starting glass at 1000rpm for 30 seconds. After annealing at 51 ℃ for 30 seconds, the material was exposed to polarized UV light (band pass filter at 365 nm) at 51 ℃ under nitrogen atmosphere at 120mWcm^-2Lasting 40 seconds. The resulting polymer film had the following characteristics.

Film thickness 3.93 μm

Δn＝0.0358

The retardation curve of the polymer film is shown in fig. 2, where the retardation is plotted against the viewing angle. As can be seen from fig. 2, the retardation curve has a maximum at a viewing angle of 0 °. The retardation curve is typically an "a-plate" in which the ordinary axis (also referred to as the "a-axis") of the LC material is oriented perpendicular to the plane of the layer, i.e. parallel to the normal direction of the incident light.

Example 2

The following polymerizable liquid crystalline materials were prepared

Clearing the bright spots: 48.5 deg.C

The polymerizable liquid crystalline material was spin coated onto the starting glass at 1000rpm for 30 seconds. Thereafter, the material was exposed to polarized UV light (band pass filter at 365 nm) at 53 ℃ under nitrogen atmosphere at 120mWcm^-2Lasting 40 seconds. The resulting polymer film had the following characteristics.

Film thickness 3.03 μm

Δn＝0.0253

The retardation curve of the polymer film is shown in fig. 3, where the retardation is plotted against the viewing angle. As can be seen from fig. 3, the retardation curve has a maximum at a viewing angle of 0 °. The retardation curve is typically an "a-plate" in which the ordinary axis (also referred to as the "a-axis") of the LC material is oriented perpendicular to the plane of the layer, i.e. parallel to the normal direction of the incident light.

Example 3

The following polymerizable liquid crystalline materials were prepared

Clearing the bright spots: 41.9 deg.C

The polymerizable liquid crystalline material was spin coated onto the starting glass at 600rpm for 30 seconds. Then, willThe material was exposed to polarized UV light (band pass filter at 365 nm) at 43 ℃ under nitrogen atmosphere at 35mWcm^-2Lasting 30 seconds. The resulting polymer film had the following characteristics.

The retardation curve of the polymer film is shown in fig. 4, where the retardation is plotted against viewing angle. As can be seen from fig. 4, the retardation curve has a maximum at a viewing angle of 0 °. The retardation curve is typically an "a-plate" in which the ordinary axis (also referred to as the "a-axis") of the LC material is oriented perpendicular to the plane of the layer, i.e. parallel to the normal direction of the incident light.

Example 4: angular dependence of the radiation source

Clearing the bright spots: 48.9 deg.C

The polymerizable liquid crystalline material was spin coated onto the starting glass at 1000rpm for 30 seconds. The material was then exposed to polarized UV light (365nm bandpass filter), each at different radiation source tilt angles (40 °, 50 °, 60 °, 70 ° and 90 °), at 51 ℃ under nitrogen atmosphere at 50mWcm^-2Lasting 30 seconds. The resulting polymer film had the following characteristics.

Film thickness 3.31 μm

Δn＝0.0272

The retardation curve of the polymer film is shown in fig. 5, where the retardation is plotted against the viewing angle. As can be seen from fig. 5, the retardation curve has a maximum at a viewing angle of 0 ° for the polymer film obtained by irradiation at an angle of 90 ° (see α in fig. 1). The retardation curve is typically an "a-plate" in which the ordinary axis (also referred to as the "a-axis") of the LC material is oriented perpendicular to the plane of the layer, i.e. parallel to the normal direction of the incident light. The retardation curve changes stepwise from an "a-plate" retardation curve (see 90 °) to a typical "O-plate" retardation curve (see 50 ° or 40 °) depending on the radiation angle (α in fig. 1). In an "O-plate" the extraordinary axis of the LC material is tilted with respect to the plane of the layer, resulting here in a retardation maximum at a viewing angle of-60 °.

Claims (28)

1. A method of making a polymer film comprising the steps of:

a) providing a layer of a polymerizable liquid crystalline material comprising at least one dichroic photoinitiator on a substrate,

b) liquid crystal material in its isotropic phase upon irradiation with linearly polarized light, and

c) optionally removing the polymerized film from the substrate.

2. A method according to claim 1, wherein step b) is carried out at a temperature of 1-5 ℃ above the clear point of the liquid crystal material.

3. A method according to claim 1 or 2, characterized in that the polymerizable liquid crystal material comprises at least one mono-, di-or multireactive polymerizable mesogenic compound, and at least one dichroic photoinitiator.

4. A method according to claim 1 or 2, characterized in that the polymerizable liquid crystal material comprises at least one mono-reactive polymerizable mesogenic compound, at least one di-or multireactive polymerizable mesogenic compound, and at least one dichroic photoinitiator.

5. A method according to claim 1 or 2, characterized in that the polymerizable liquid crystal material comprises at least one mono-reactive chiral polymerizable mesogenic compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound, and at least one dichroic photoinitiator.

6. A method according to claim 1 or 2, characterized in that the polymerizable liquid crystal material comprises at least one di-or multireactive chiral polymerizable mesogenic compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound, and at least one dichroic photoinitiator.

7. A method according to claim 1 or 2, characterized in that the polymerizable liquid crystal material comprises at least one non-polymerizable chiral compound, at least one mono-, di-or multireactive achiral polymerizable mesogenic compound, and at least one dichroic photoinitiator.

8. The method according to claim 1 or 2, wherein the dichroic photoinitiator is selected from compounds of formula I,

wherein

P is a polymerizable group, and P is a polymerizable group,

sp is a spacer group or a single bond,

A¹¹in each case independently of one another in a plurality of occurrences is an aryl, heteroaryl, aliphatic or heterocyclic radical, which is optionally substituted by one or more identical or different radicals L,

Z¹¹independently of one another at each occurrence, -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR⁰¹-、-NR⁰¹-CO-、-NR⁰¹-CO-NR⁰²、-NR⁰¹-CO-O-、-O-CO-NR⁰¹-、-OCH₂-、-CH₂O-、-SCH₂-、-CH₂S-、-CF₂O-、-OCF₂-、-CF₂S-、-SCF₂-、-CH₂CH₂-、-(CH₂)₄-、-CF₂CH₂-、-CH₂CF₂-、-CF₂CF₂-、-CH＝N-,-N＝CH-、-N＝N-、-CH＝CR⁰¹-、-CY⁰¹＝CY⁰²-, -C.ident.C-, -CH-COO-, -OCO-CH-or a single bond,

m is 0,1, 2 or 3,

r is 0,1, 2,3 or 4,

l is, independently of one another in each case in a plurality of occurrences, H, F, Cl, CN or optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 5C atoms,

R^11-13independently of one another, H, halogen, CN, NO₂，NCS，SF₅P-Sp-or a linear or branched alkyl group having 1 to 20C atoms, optionally mono-or polysubstituted with F, Cl, Br, I or CN, and wherein one or more non-adjacent CH groups₂The radicals being in each case independently of one another optionally substituted by-O-, -S-, -NR-⁰¹-、-SiR⁰¹R⁰²-、-CO-、-COO-、-OCO-、-OCO-O-、-NR⁰¹-CO-、-CO-NR⁰¹-、-NR⁰¹-CO-NR⁰²-、-S-CO-、-CO-S-、-CY⁰¹＝CY⁰²-or-C.ident.C-is replaced in such a way that O and/or S atoms are not directly linked to each other, and

Y⁰¹and Y⁰²Each independently of the others, represents H, F, Cl or CN,

R⁰¹and R⁰²Independently of one another, H, or a linear or branched alkyl group having 1 to 20C atoms.

9. A method according to claim 1 or 2, wherein the proportion of the dichroic photoinitiator in the total liquid crystal material is in the range of 1-20 wt%.

10. The method according to claim 1 or 2, characterized in that the substrate is TAC, PET, PVA, PE film or glass plate.

11. A method according to claim 1 or 2, wherein step b) is performed by exposing the polymerizable liquid crystal material to linearly polarised UV radiation.

12. The method of claim 1 or 2, wherein the polymer film has a Δ n in the range of 0.01 to 0.30.

13. The method according to claim 11, characterized in that the power of the UV radiation is between 5 and 200mW cm^-2Within the range.

14. The method of claim 11, wherein the dose of UV is between 25 and 7200mJ cm^-2Within the range.

15. A method according to claim 1 or 2, wherein the polymerisable liquid crystal material is aligned in a planar orientation with respect to the main substrate plane.

16. A method according to claim 1 or 2, wherein the polymerizable liquid crystal material is aligned in a tilted orientation of >0 ° and <90 ° with respect to the main plane of the substrate.

17. Method according to claim 1 or 2, characterized in that the irradiation in step b) is carried out at an oblique angle of >0 ° and <90 ° with respect to the main plane of the substrate.

18. The method according to claim 1 or 2, wherein the thickness of the polymer film is in the range of 3 to 30 μm.

19. The method of claim 1 or 2, wherein the polymer film has an optical retardation of less than 200 nm.

20. A polymer film obtained according to the method of any one of claims 1 to 19.

21. Use of a polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19 as alignment layer or optical retardation film in Liquid Crystal Displays (LCD) or other optical or electro-optical devices for decorative or security applications.

22. Use of the polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19 as a retardation film or compensation film in an optical device.

23. Use according to claim 22, wherein the optical device is a liquid crystal display.

24. Use of a polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19 as alignment layer in an optical device.

25. Use according to claim 24, wherein the optical device is a liquid crystal display.

26. Use of a polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19 for decorative or security applications.

27. Compensator comprising at least one polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19.

28. Liquid crystal display comprising at least one polymer film according to claim 20 or obtained according to the process of any one of claims 1 to 19 or a compensator according to claim 27.